CVD TiSiN barrier for copper integration

ABSTRACT

The present invention provides a method of forming a titanium silicon nitride barrier layer on a semiconductor wafer, comprising the steps of depositing a titanium nitride layer on the semiconductor wafer; plasma-treating the titanium nitride layer in a N 2 /H 2  plasma; and exposing the plasma-treated titanium nitride layer to a silane ambient, wherein silicon is incorporated into the titanium nitride layer as silicon nitride thereby forming a titanium silicon nitride barrier layer. Additionally, there is provided a method of improving the barrier performance of a titanium nitride layer comprising the step of introducing silicon into the titanium nitride layer such that the silicon is incorporated into the titanium nitride layer as silicon nitride. Also provided is a method of integrating copper into a semiconductor device and a method of improving copper wettability at a copper/titanium nitride interface in a semiconductor device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the field of semiconductormanufacturing. More specifically, the present invention relates to amethod of achieving low contact resistance and to improving titaniumnitride barrier performance for copper integration.

2. Description of the Related Art

With the down-scaling and increased speed of semiconductor devices beingfabricated currently and with the levels of integration in VLSI and ULSIintegrated chips, metallization processes require low resistance metals.Traditionally, aluminum has been used for interconnects in semiconductordevices, but recently, copper, with its lower resistance and betterelectromigration lifetime than that of aluminum, has been used forintegration. However, copper is very mobile in many of the materialsused to fabricate semiconductor devices. Copper can diffuse quicklythrough certain materials including dielectrics such as oxides. Thiscauses damage to nearby devices on the semiconductor substrate. Thus, itis necessary to have copper barrier layers in place to avoid any copperdiffusion within the semiconductor device.

Titanium nitride layers can serve as barrier layers against diffusion,including copper diffusion, in semiconductor device structures, e.g.,contacts, vias and trenches. Deposition of an effective and useabletitanium nitride barrier layer realizes good step coverage, sufficientbarrier thickness at the bottom of device features and a conformal filmhaving a smooth surface for further processing steps. However the TiNbarrier layer must be as thin as possible to accommodate the higheraspect ratios of today's devices. Additionally, the TiN barrier layermust be inert and must not adversely react with adjacent materialsduring subsequent thermal cycles, must prevent the diffusion ormigration of adjacent materials through it, must have low resistivity(exhibit high conductivity), low contact or via resistance and lowjunction leakage.

Titanium nitride layers can be deposited on a wafer by the rapid thermalnitridation of a titanium layer or by any deposition process, e.g.,sputtering (PVD) and CVD. CVD deposition of titanium nitride barrierfilms eliminates the problems with metal reliability and junctionleakage associated with PVD deposited TiN barrier films and isconsidered a cleaner process than PVD TiN. Additionally, the CVD processproduces conformal films with good step coverage in the 0.35 micron orless structures found in state of the art VLSI and ULSI devices. In aCVD process a metalorganic precursor such as tetrakisdimethylaminotitanium (TDMAT) or tetrakisdiethylamino titanium (TDEAT) is thermallydecomposed to deposit a titanium nitride layer.

However, MO CVD TiN does not have as good barrier performance to copperdiffusion as, for example, IMP tantalum or IMP tantalum nitride. Thisfilm contains carbon and is a porous film that easily absorbs oxygenthereby becoming highly resistive and unstable. It is critical to havean effective barrier with copper metallization. Electromigration ofcopper into the silicon substrate ruins device performance.

Barrier performance of a TiN film can be improved by altering the methodof deposition and/or the components of the film. Titanium nitridesputtered by using high density plasma techniques, such as those where arelatively large proportion of the material sputtered from the target isionized and electrically attracted to the substrate, has produced smoothconformal films with low resistivity for subsequent aluminum depositionthereon. Titanium-silicon-nitrogen compounds provide a better diffusionbarrier for aluminum or copper interconnects than titanium nitridebarriers. Silane is used to incorporate silicon into a MOCVD TiN film insuch a manner that a silicon rich surface is formed on the titaniumnitride. This method does not utilize an in situ plasma step to furtherimprove the film properties of the titianium nitride layer and thesilicon is primarily deposited on the surface of the underlying titaniumnitride layer.

Additionally, a high temperature method to deposit a porous titaniumnitride layer with subsequent exposure firstly to a silicon-containinggas ambient and secondly to a low plasma power generated N₂/H₂ plasmaincorporates silicon, as silicon nitride, primarily on the surface ofthe titanium nitride film. However, lower wafer temperatures aredesired, as previously deposited material may have critical heat andtemperature limitations. For example, current generation low kdielectric materials require wafer temperatures below approximately<380-400 ° C. Also, higher rf power can provide for efficient filmtreatment realizing low film resistivity and via resisance and providingfor faster throughput. Thus, there exists a need in the art to furtherimprove the barrier performance of titanium films for subsequent copperintegration.

Therefore, a need exists for an improved effective means of improvingtitanium nitride barrier performance for copper integration.Specifically, there is a lack of effective means of incorporatingsilicon as silicon nitride into a titanium nitride layer therebyimproving barrier performance for copper integration. The presentinvention fulfills these long-standing needs and desires in the art.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a method of forming atitanium silicon nitride barrier layer on a semiconductor wafer,comprising the steps of depositing a titanium nitride layer on thesemiconductor wafer; plasma-treating the titanium nitride layer in aN₂/H₂ plasma; and exposing the plasma-treated titanium nitride layer toa silicon-containing gas ambient, wherein silicon is incorporated intothe titanium nitride layer as silicon nitride thereby forming a titaniumsilicon nitride barrier layer.

Another embodiment of the present invention provides a method of forminga titanium silicon nitride barrier layer on a semiconductor wafer,comprising the steps of vaporizing a tetrakisdimethylamino titanium;introducing the vaporized tetrakisdimethylamino titanium into adeposition chamber of a CVD apparatus; maintaining the depositionchamber at a pressure of about 5 Torr and the wafer at a temperature ofabout 360° C.; thermally decomposing the tetrakisdimethylamino titaniumgas in the deposition chamber; vapor-depositing the titanium nitridefilm onto the wafer; plasma-treating the titanium nitride layer in aN₂/H₂ plasma at a plasma power of about 750W for about 35 secondswherein a single titanium nitride layer having a thickness of about 50 Åis formed; and exposing the plasma-treated titanium nitride layer to asilane gas ambient for about 10 seconds, wherein silicon is incorporatedinto the titanium nitride layer as silicon nitride thereby forming atitanium silicon nitride barrier layer.

Yet another embodiment of the present invention provides a method ofimproving the barrier performance of a titanium nitride layer comprisingthe step of introducing silicon into the titanium nitride layer suchthat the silicon is incorporated into the titanium nitride layer assilicon nitride wherein the barrier performance of the titanium nitridelayer is improved.

In yet another embodiment of the present invention there is provided amethod of improving the barrier performance of a titanium nitride layercomprising the steps of vaporizing tetrakisdimethyl amino titanium;introducing the vaporized tetrakisdimethylamino titanium into adeposition chamber of a CVD apparatus; maintaining the depositionchamber at a pressure of about 5 Torr and the wafer at a temperature ofabout 360° C.; thermally decomposing the tetrakisdimethylamino titaniumgas in the deposition chamber; vapor-depositing the titanium nitridefilm onto the wafer; plasma-treating the titanium nitride layer in aN₂/H₂ plasma at a plasma power of about 750W for about 35 secondswherein a single titanium nitride layer having a thickness of about 50 Åis formed; and exposing the plasma-treated titanium nitride layer to asilane gas ambient for about 10 seconds, wherein silicon is incorporatedinto the titanium nitride layer as silicon nitride thereby improving thebarrier performance of the titanium nitride layer.

In yet another embodiment of the present invention there is provided amethod of integrating copper into a semiconductor device comprising thesteps of forming a titanium silicon nitride barrier in a feature of thesemiconductor device by the methods disclosed supra and depositing acopper layer over the titanium silicon nitride barrier therebyintegrating copper into the semiconductor device.

In yet another embodiment of the present invention there is provided amethod of improving copper wettability at an interface of a copper layerand a titanium nitride layer in a semiconductor device comprising thesteps of introducing silicon into the titanium nitride layer as siliconnitride by the methods disclosed supra such that that a titanium siliconnitride layer is formed; and depositing a copper layer over the titaniumsilicon nitride layer wherein copper wettability at the interface of thecopper layer and the titanium silicon nitride layer is improved overcopper wettability at the copper/titanium nitride interface.

Other and further aspects, features, and advantages of the presentinvention will be apparent from the following description of theembodiments of the invention given for the purpose of disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the matter in which the above-recited features, advantages andobjects of the invention, as well as others which will become clear, areattained and can be understood in detail, more particular descriptionsof the invention briefly summarized above may be had by reference tocertain embodiments thereof which are illustrated in the appendeddrawings. These drawings form a part of the specification. It is to benoted, however, that the appended drawings illustrate embodiments of theinvention and therefore are not to be considered limiting in theirscope.

FIG. 1 is a partial schematic of a HP+TxZ chamber slowing how the silaneline is introduced into the chamber through a line separate from that ofnitrogen (FIG. 1A) and of the HP+TxZ modified chamber lid showing thetwo gas line spaces for silane and nitrogen in the gas box (FIG. 1B).

FIG. 2 is a flow diagram of the MOCVD TiSiN process.

FIG. 3 shows silane flow-time experiments measuring sheet resistance asthe duration of air exposure increases for differing silane exposuretimes. Films are plasma treated for 30 secs. FIG. 3A: 30 sccm SiH4, 100sccm N2 and 1.3 Torr. FIG. 3B: 80 sccm SiH4, 300 sccm N2 and 2 Torr.

FIG. 4 measures sheet resistance as the duration of the silane treatmentincreases for plasma treated TiN film (FIG. 4A) and non-plasma treatedTiN film (FIG. 4B) initially after silane treatment and after a day ofair exposure. Silane treatment was performed with a flow rate of 30 sccmsilane under 1.3 Torr pressure. Plasma exposure was 35 sec.

FIG. 5 shows a TEM of the bottom and corner coverage before and after asilane soak of the titanium nitride film.

FIG. 6 shows a void-free 0.17 μm ECP copper fill at an aspect ratio of10:1 with 1×50 Å TiSiN. Barrier/Seed: degas/100 Å pre-clean/50 ÅTiSiN/2000 Å SIP copper.

FIG. 7 depicts the wettability of 200 Å copper on 1×50 Å TiN (FIG. 7A)and on 1×50 Å TiSiN (FIG. 7B). Copper film is annealed at 380° C. for 15min.

FIG. 8 shows the percent change in sheet resistance of annealed 500 ÅSIP copper on TiSiN with increasing silane exposure. Process conditionsare 80 sccm SiH4, 300 sccm N2 and 2 Torr.

FIG. 9 is a SIMS profile of copper diffusion through TiSiN plasmatreated for various times and then silane. Film stack: 500 Å SIP Cu/50 ÅTiN (split)/3 kÅ oxide/Si, annealed at 380° C. for 30 min.

FIG. 10 shows the WIW and WTW sheet resistance uniformity for 1×50 ÅTiSiN films (FIG. 10A) and 1×35 Å TiSiN films (FIG. 10B) for a 5000wafer run. Wafers had a 3 mm edge exclusion.

FIG. 11 shows the WIW and WTW thickness uniformity for 1×50 Å TiSiNfilms (FIG. 11A) and 1×35 Å TiSiN films (FIG. 11B) for a 5000 wafer run.Thicknesses are calculated from XRF intensities.

FIG. 12 shows the average mechanical and system adders (FIG. 12A) andthe average in-film particles and system adders (FIG. 12B) at >0.16 μmfor a 5000 wafer run.

FIG. 13 shows the effect of one hour of chamber idle time on waferprocessing for the sheet resistance and resistance uniformity (FIG. 13A)and the film thickness (FIG. 13B) for 1×50 Å film.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of the present invention provides a method of forming atitanium silicon nitride barrier layer on a semiconductor wafer,comprising the steps of depositing a titanium nitride layer on thesemiconductor wafer; plasma-treating the titanium nitride layer in aN₂/H₂ plasma; and exposing the plasma-treated titanium nitride layer toa silane ambient, wherein silicon is incorporated into the titaniumnitride layer as silicon nitride thereby forming a titanium siliconnitride barrier layer.

In one aspect of this embodiment the titanium nitride layer is depositedby a method comprising the steps of vaporizing a metalorganictitanium/nitrogen-containing compound; introducing the vaporizedtitanium/nitrogen-containing compound into a deposition chamber of a CVDapparatus; maintaining the deposition chamber at a pressure and thewafer at a temperature suitable for the high pressure chemical vapordeposition of the titanium nitride film onto the wafer; thermallydecomposing the titanium/nitrogen-containing gas in the depositionchamber; and vapor-depositing the titanium nitride film onto the wafer.

In this aspect of the present invention the metalorganic compound may betetrakisdimethylamino titanium or tetrakisdiethylamino titanium. Thedeposited titanium nitride layer can have a thickness of 5 Å to 100 Å. Arepresentative thickness is about 50 Å. Generally, the depositionchamber pressure can be from about 1 Torr to about 10 Torr. Arepresentative example is 5 Torr. The wafer temperature can be fromabout 320 ° C. to about 420° C. A representative example is about 360°C. The titanium nitride layer is plasma treated at a plasma power ofabout 600 to about 1500W. A representative example is about 750W plasmatreatment in about 15 seconds to about 40 seconds with 35 seconds beinga representative example. The silicon-containing gas may be silane,disilane, methylsilane, or dimethylsilane. Exposure to thesilicon-containing gas ambient is from about 4 seconds to about 20seconds with ten seconds as a representative example for duration ofexposure.

In another aspect of this embodiment of the present invention thetitanium nitride layer may be deposited and plasma-treated incrementallywithout an intervening step prior to exposure of the layer to a silaneambient. A representative number of such cycles is two with both cyclesdepositing a titanium nitride layer having a thickness of about 5 Å toabout 50 Å with 25 Å being a representative example. Plasma treatment ofthese titanium nitride layers is from about 5 seconds to 30 seconds with15 seconds being a representative example.

Another embodiment of the present invention provides a method of forminga titanium silicon nitride barrier layer on a semiconductor wafer,comprising the steps of vaporizing tetrakisdimethylamino titanium;introducing the vaporized tetrakisdimethylamino titanium into adeposition chamber of a CVD apparatus; maintaining the depositionchamber at a pressure of about 5 Torr and the wafer at a temperature ofabout 360° C.; thermally decomposing the tetrakisdimethylamino titaniumgas in the deposition chamber; vapor-depositing the titanium nitridefilm onto the wafer; plasma-treating the titanium nitride layer in aN₂/H₂ plasma at a plasma power of about 750W for about 35 secondswherein a single titanium nitride layer having a thickness of about 50 Åis formed; and exposing the plasma-treated titanium nitride layer to asilane gas ambient for about 10 seconds, wherein silicon is incorporatedinto the titanium nitride layer as silicon nitride thereby forming atitanium silicon nitride barrier layer.

Yet another embodiment of the present invention provides a method ofimproving the barrier performance of a titanium nitride layer comprisingthe step of introducing silicon into the titanium nitride layer suchthat the silicon is incorporated into the titanium nitride layer assilicon nitride so that the barrier performance of the titanium nitridelayer is improved. The titanium nitride layer and the incorporation ofsilicon as silicon nitride therein can be accomplished by the methodsdisclosed supra.

In an aspect of this embodiment of the present invention the titaniumnitride layer may be deposited and plasma-treated incrementally withoutan intervening step prior to exposure of the layer to a silane ambientusing the methods and examples disclosed supra for such incrementaldeposition.

In yet another embodiment of the present invention there is provided amethod of improving the barrier performance of a titanium nitride layercomprising the steps of vaporizing tetrakisdimethylamino titanium;introducing the vaporized tetrakisdimethylamino titanium into adeposition chamber of a CVD apparatus; maintaining the depositionchamber at a pressure of about 5 Torr and the wafer at a temperature ofabout 360° C.; thermally decomposing the tetrakisdimethylamino titaniumgas in the deposition chamber; vapor-depositing the titanium nitridefilm onto the wafer; plasma-treating the titanium nitride layer in aN₂/H₂ plasma at a plasma power of about 750 W for about 35 secondswherein a single titanium nitride layer having a thickness of about 50 Åis formed; and exposing the plasma-treated titanium nitride layer to asilane gas ambient for about 10 seconds, wherein silicon is incorporatedinto the titanium nitride layer as silicon nitride thereby improving thebarrier performance of the titanium nitride layer.

In yet another embodiment of the present invention provides a method ofintegrating copper into a semiconductor device comprising the steps offorming a titanium silicon nitride barrier in a feature of thesemiconductor device by the methods disclosed supra and depositing acopper layer over the titanium silicon nitride barrier therebyintegrating copper into the semiconductor device.

In yet another embodiment of the present invention there is provided amethod of improving copper wettability at an interface of a copper layerand a titanium nitride layer in a semiconductor device comprising thesteps of introducing silicon into the titanium nitride layer as siliconnitride by the methods disclosed supra such that a titanium siliconnitride layer is formed; and depositing a copper layer over the titaniumsilicon nitride layer wherein copper wettability at the interface of thecopper layer and the titanium silicon nitride layer is improved overcopper wettability at the copper/titanium nitride interface.

Barrier performance of a titanium nitride layer is improved with theaddition of silicon, as primarily SiN, inside the TiN layer. This isaccomplished by exposing the titanium nitride film to a silicon-containggas ambient. Such an ambient can be a silane, a disilane, amethylsilane, or a dimethylsilane ambient. A silane soak of the titaniumnitride layer allows silicon to be incorporated into the layer to formthe silicon nitride. However, the plasma duration and the silanetreatment need to be adjusted in order to incorporate the silicon assilicon nitride and not free silicon. The TiN treatment is optimized toallow the silane to react fully with the film where the precursor is notfully reacted but not to degrade copper resistivity.

The silane reacts with the non-fully reacted molecule of TDMATincorporated into the film. It breaks the N—C bond and forms a SiN bondin the film. Non-fully reacted means that, during the thermaldecomposition of the precursor TDMAT, not all of the CH3 groups areeliminated, thus TiNCH₃ bonds remain in the film. During the plasmatreatment the concentration in carbon decreases because the NCH₃ groupsare replaced by the nitrogen from the plasma. Therefore a plasma treatedfilm reacts less with silane than a non-plasma treated film.

In order to achieve a good barrier, SiN bonds in the amorphous matrixaround the TiN nanocrystallite need to be maximized, but at the sametime unreacted silane needs to be prevented from subsequently reactingwith the copper and thereby forming a solid solution of copper andsilicon or, even worse, a precipitate of copper silicide as bothcompounds have high resistivity.

If this is not the case, the silicon migrates during annealing insidethe copper which leads to poor contact resistance. However, if the TiNis not plasma treated sufficiently, carbon remains in the film and thematerial resistivity remains high and results in high contactresistance. Both plasma duration as well as the silane treatmentconditions (duration, dilution and pressure) must be optimized in orderto minimize the contact resistance impact of silane treatment and toachieve the best barrier properties.

The following examples are given for the purpose of illustrating variousembodiments of the invention and are not meant to limit the presentinvention in any fashion.

EXAMPLE 1

200 mm TxZ Chamber Modifications

A high-pressure process in a standard Applied Materials TxZ chamber isused for formation of the titanium nitride barrier layer.Low-resistivity titanium nitride thin-films are thermally depositedusing a high-pressure MOCVD process. TDMAT is currently used as aprecursor although TDEAT, among others, can also be used. The TiN thinfilm is subsequently plasma post treated with an H₂/N₂ plasma generatedby a high plasma power of from 600 to 1500 Watts in order to reduce thefilm resistivity. Following the plasma post treatment, the layer isexposed to a silane soak.

In order to accomplish this TiSiN process, the hardware is built basedon a TxZ chamber where SiH₄ is introduced through a second line into thechamber separate from the TDMAT line (FIG. 1A). In this configurationthe 200 mm TxZ gas box has two gas line spaces for silane and nitrogen.The chamber lid is modified so that the gas pass through partsaccommodate silane gas separately via a second gas feed (FIG. 1B).

The TxZ chamber hardware is also modified to include an independent linewith purge capability. Thus, pump purge time is optimized and silaneresidue in the chamber is avoided. This residue reacts with the copperat the surface of the next wafer and causes particle formation and highresistivity. The chamber can be set up as follows:

Precursors: TDMAT TDEAT

Carrier gases: Ar, N2, He

Chamber pressure: 1 to 10 Torr

Wafer temperature: 320° C. to 370° C.

EXAMPLE 1

Overview of the Formation of TiSiN Barrier Layer

The formation of the TiSiN barrier layer comprises a basic three stepprocess as shown in FIG. 2. TDMAT is vaporized and, upon heating of thewafer, is thermally decomposed as a film deposited on the wafer at a lowtemperature of about 360° C. which corresponds to a heater temperatureof about 380° C. and at a high chamber pressure of 5 Torr. The processcan be run with low wafer temperatures ranging from about 320° C. toabout 370° C. and chamber pressures ranging from about 1 to about 10Torr.

The decomposition rate of TDMAT is controlled by various processconditions. The step coverage and the deposition rates depend on thewafer temperature. As the decomposition of TDMAT is a pyrolytic process,the rate of decomposition and thereby the rate of depositon on the waferincreases with the wafer temperature. It is possible to compensate forthe loss in deposition rate at a low temperature by an increase inprecursor delivery. The deposition temperature is dependant on the typeof application, e.g., the type of low K dielectric needed. However, aspacing change affects wafer temperature and thus the deposition rate isaffected. Concomitantly, an increase in chamber pressure and/or anincrease in TDMAT flow will increase the deposition rate. Additionally,increasing the N₂ or He carrier gas dilution flow will decrease thedeposition rate.

The resultant deposited film comprises TiN(C). The TiN(C) film istreated with a low frequency 350 kHz induced N₂/H₂ plasma generated by ahigh plasma power of 750 W. Such treatment reduces carbon concentrationas described supra. The plasma treatment duration depends on thethickness of the TiN(C) film deposited. For a targeted thickness of 50 Å(1×50 process) the plasma treatment is about 35 s with a range of about4 seconds to 40 seconds for titanium nitride thicknesses of about 5 Å toabout 1000 Å.

A film can be deposited incrementally until the desired thickness isreached by repeating the thermal decomposition/deposition andplasma-treating steps. The plasma treatment duration depends on thethickness of the deposited film; each incremental thickness ranging fromabout 5 Å to about 50 Å with concomitant plasma treatment times of about5 seconds to about 30 seconds. Additionally, a 50 Å film can bedeposited in a 2×25 process. Here a layer of about 25 Å is deposited andsubsequently plasma-treated for about 15 s, the deposition step isrepeated for another 25 Å layer followed by another plasma treatment.

The TiN film is subsequently exposed to a silicon-containing gas ambientsuch as a silane soak to yield a TiSiN film having the silicon primarilyincorporated as silicon nitride. The silane treatment is performed at apressure from about 0.8 Torr to about 5 Torr. Little effect on theefficacy of the silane treatment is found due to the pressure. Apressure of about 1.3 Torr to about 2 Torr is used because, at thesepressures, the delta pressure between the front and the back of thewafer is sufficient to vacuum chuck the wafer and avoid any wafermotion; 2 Torr provide better chucking efficiency. It is important tohave a stable regime and not a transient one for this process. In thetransition from the plasma treatment step to the silane treatment stepthe plasma treatment pressure needs to reduce or increase to the silanetreatment pressure where silane flow is below 100 sccm and wheretreatment time is for only 10 s. A stable regime for these changes inconditions provides for reproducibility in the process.

EXAMPLE 2

XPS Analysis of a TiSiN Film

An X-ray photoelectron spectroscopy depth profile of a TiSiN layer withand without the N₂/H₂ plasma treatment is shown in Table 1. The oxygenfound in the plasma treated TiSiN film is due to air exposure of thewafer samples. The pre-plasma TiN layer as deposited is very porous andamorphous. Plasma treatment of this layer transforms the amorphous filminto a nanocrystalline film that is denser. Thus, plasma treatmenteliminates the majority of carbon and oxygen from the film, the altereddenser crystalline structure allows less silicon incorporation intoplasma treated films.

TABLE 1 Film Composition (%) Ti N C O Si TiSiN No Plasma 28.5 21.2 28.814.5 7.0 TiSiN Plasma 40.5 48.2 5.6 1.4 4.4

An XPS profile can only show the elemental composition of the film andnot how the elemental components are bonded within the film. Table 2shows the possible bonding states of the elements in the TiSiN filmwithout a plasma treatment prior to the silane soak or with said plasmatreatment.

TABLE 2 Bonding State of Each Element TiSiN No Plasma TiSiN Plasma TiTiN & TiN & TiCx (TiCx &/or TiOx) N TiN TiN & N—C—H C TiCx & C—C & (C—H)TiCx O TiOx &/or TiCxOy — Si SixNy SixNy

TDMAT is thermally decomposed at 360° C. and the decomposition productsare deposited on the substrate. The decomposition reaction is:

Other hydrocarbons may be formed during this pyrolytic process. Notethat oxygen is not an elemental byproduct of the pyrolytic decompositionof TDMAT. Oxygen is incorporated into the untreated film when the waferis exposed to air.

The N₂/H₂ plasma treatment of the deposited film significantly reducescarbon and oxygen levels within the film. This creates a layercomprising TiCxNyHz which yields byproducts CxHy+HNR₂ that aresubsequently pumped out of the chamber system. This scheme assumes thatoxygen is not incorporated into the system. The resulting plasma-treatedTiN film comprises a layer that is 50-60% of the as deposited thickness.

EXAMPLE 3

Silane Treatment vs. Sheet Resistance

In situ plasma treatment of TiN films improves film properties. TheN₂/H₂ plasma treatment significantly reduces the amounts of carbon andoxygen in the film and thereby lowers resistivity. The post-treatmentsilane soak after standard MOCVD TiN deposition improves barrierproperties. The silicon, as SiN, incorporated into the TiN film reducesoxidation of the film upon exposure to air also reducing resistivity ofthe TiSiN barrier layer.

TiN plasma-treated films exposed to silane for increasing amounts oftime are tested for sheet resistance after air exposure (FIGS. 3A & 3B).The resistivity of a 1×50 Å film is reduced from about 650 μΩ-cm tobelow 600 μΩ-cm with silane exposure. Resistivity reduction stabilizesfor ten seconds of silane exposure or more. FIG. 3B reinforces theimportance of selection of the proper silane treatment conditions;higher silane flow and dilution achieves a higher front pressure of 2Torr and is in a stable regime during the silane treatment of the waferfor chucking performances. A five second silane treatment at the higherflow rates and pressure of FIG. 3B resulted in a higher sheet resistancefor any length of air exposure in comparison to the conditions used inFIG. 3A.

A silane soak reduces measured resistivity of both treated and untreatedfilm. The sheet resistance of a TiN film plasma treated for 35 secs(FIG. 4A) is significantly less than that of the untreated TiN film(FIG. 4B) for any length of silane treatment duration. Again sheetresistance levels stabilize after about ten seconds of silane treatment.Sheet resistance after a day of air exposure is also measured. Thisdemonstrates that the combination of a N₂/H₂ plasma treatment and apost-treatment silane soak is more effective at reducing oxidation andmaintaining a lower sheet resistance of the film than a silane soak ofan untreated TiN film.

EXAMPLE 4

Reduction of Sidewall Thickness

A silane soak of a TiN film improves sidewall barrier properties; italso improves film stability of the sidewall, especially the lesstreated sidewall. A silane treatment reduces TiN sidewall thickness.FIG. 5 is a transmission electron micrograph showing that silanetreatment of a plasma-treated TiN film yields good bottom and cornercoverage and reduces the sidewall thickness from 68 Å to 52 Å. It isalso apparent from the TEM that silane treatment of a TiN film producesa TiSiN film with good step coverage and a continuous smooth morphologyalong the bottom and sidewalls of the structure.

EXAMPLE 5

CVD TiSiN as a Copper Barrier Layer

The continuous and smooth morphology of TiSiN films enhance theself-ionizing plasma (SIP) deposition of copper seed with electroplating(ECP) filling capability. FIG. 6 shows that an electroplating fill of 2kÅ SIP copper on 1×50 Å TiSiN barrier can be void free in a 0.17 μm 10:1aspect ratio structure. It is necessary to consider copper wettabilityat the Cu/barrier interface since this interface is the primary path forcopper migration. Wettability of copper is also enhanced with a 1×50 ÅTiNiS barrier layer. A 200 Å copper film annealed at 380° C. for 15 min.on 1×50 Å TiN showed dewetting (FIG. 7A) whereas the same copper film ona 1×50 Å TiNiS layer demonstrates no dewetting (FIG. 7B).

EXAMPLE 6

Sheet Resistance of Annealed SIP Copper on TiSiN

Silane treatment of TiN films improves the barrier properties of thefilms. However, an over-extended silane treatment of the TiN film candegrade copper resistivity causing the silicon to migrate inside thecopper during annealing and thus leading to poor contact resistance.However if the TiN is not treated sufficiently, the material resistivityremains high and will give high contact resistance.

FIG. 8 shows the percent change in sheet resistance with increasingsilane exposure of an annealed 500 Å SIP copper. The copper was annealedat 380° C. for 15 min. The percent change in copper Rs on standard MOCVDTiN is about 26%. The copper sheet resistance is reduced after theanneal in all cases and the percent change decreases with increasingsilane exposure.

EXAMPLE 7

TiSiN Barrier Performance Against Copper Diffusion

TiSiN showed good barrier properties for oxide. A SIMS profile of anannealed SIP Cu/TiSiN/oxide stack demonstrates that silane soaked TiNlayers with or without plasma treatment significantly impeded copperdiffusion into the oxide substrate (FIG. 9). Again this demonstrates thetunable relationship between plasma-treatment duration and silanetreatment duration. The less plasma-treated layers impede copperdiffusion better than those of longer plasma treatment duration. Thebarrier efficiency is related to the formation of silicon nitride in theTiN film; i.e., as explained supra, the longer the plasma duration, theless carbon in the film and, therefore, the less SiN formed upon silaneexposure.

A comparison of actual barrier performance between TiSiN and IMP Ta 50 Åfilms in a capacitor BTS test showed similar mean-times-to-failure(MTTF) (data not shown).

EXAMPLE 8

TiSiN Adhesion on SIP Copper

IMP TaN provides an excellent barrier layer for SIP copper. Incomparison with IMP TaN, TiSiN demonstrates good adhesion on SIP copper.TiSiN on SIP copper also has similar reflectivity characteristics as SIPcopper on a TaN film. The reflectivity values for 1×50 Å TiSiN with orwithout plasma treatment but with silane treatment are practicallyidentical; it is the silane treatment, the incorporation of SiN into theTiN layer that is improving barrier properties. This is furtherreinforced by comparing the reflectivity values of a plasma treated TiNfilm with the those of the TiSiN films. Reflectivity is less than eitherthe TiSiN films or the IMP TaN film. Table 3 summarizes the results ofthe reflectivity and adhesion tests.

TABLE 3 Reflectivity and Adhesion of 500 Å SIP Copper Reflectivity*Adhesion before anneal After anneal 480 nm 436 nm IMP TaN 250 Å/SIP 500Å 132.04 119.94 Pass TiN 1 × 50 Å Plasma 35 s/SIP 500 Å 116.79 105.05Pass TiSiN 1 × 50 Å Plasma 0 s SiH4/SIP 127.79 116.13 Pass 500 Å TiSiN 1× 50 Å Plasma 35 s SiH4/ 127.09 115.88 Pass SIP 500 Å *Pass scribe andscotch tape test

EXAMPLE 9

Repeatability of TiSiN Process-5000 Wafer Run

Over the course of a 5000 wafer run the TiSiN process maintains sheetresistance uniformity (FIGS. 10A and 10B) and thickness uniformity(FIGS. 11A and 11B) for within wafer (WIW) and wafer to wafer (WTW)measurements. Comparing a 1×50 Å TiSiN film with a 1×35 Å TiSiN filmshows that the thinner film has a slightly improved sheet resistanceuniformity within wafer, but the wafer to wafer uniformity over the 5000wafer run is almost identical. The low bulk resistivity of the 1×50 ÅTiSiN film is about 273 μΩ-cm.

Thickness uniformity for the 1×50 Å and 1×35 Å TiSiN films is calculatedfrom XRF intensities. Wafer to wafer thickness uniformity for both ofthese films is excellent and is almost identical for the 5000 wafer run.Table 4 summarizes these results.

TABLE 4 UNIFORMITY Sheet Resistance Thickness TiSiN Film WIW, % WTW, %1σ WIW, % WTW, % 1σ 1 × 50 Å 6.7 2.6 — 2.3 1 × 35 Å 4.8 2.8 — 2.5

The average number of mechanical particle defects added (mechanicaladders) to a wafer after processing for a ≧0.16 μm feature remains lowfor all 5000 wafers at 9.9 (FIG. 12A). The average number of in-filmparticle defects (particle adders) is also relatively constant at 15adders for >0.16 μm feature (FIG. 12B), although since this measurementis taken after film deposition, the variation over the course of the5000 wafer run is reasonably greater than that for mechanical adders.The number of system adders for both mechanical and in-filmdeterminations is 10.

EXAMPLE 10

Effect of Chamber Idle Time

The chamber appartus used for the formation of TiSiN films exhibitsrapid chamber recovery from idle time. FIG. 13A shows that sheetresistance declines to under 600 Ω/sq and remains constant after threewafers are processed; Rs uniformity also remains constant at an averageof approximately 7%, 1 σ. FIG. 13B indicates that a 50 Å film thicknessis achieved and maintained after only three wafers. Therefore, fewwafers are lost waiting for the chamber to recover thus insuring ahigher yield.

The following references are relied upon herein:

1. J. -P. Lu. Process for Fabricating Conformal Ti—Si—N and Ti—B—N BasedBarrier Films with Low Defect Density. U.S. Ser. No. 6,017,818 (Jan. 25,2000).

2. Hsu, W. -Y., Hong, Q. -Z. and Lu, J. -P. Barrier/Liner with aSiNx-Enriched Surface Layer on MOCVD Prepared Films. U.S. Ser. No.6,037,013 (Mar. 14, 2000).

3. S. Lopatin. Low Resistivity Semiconductor Barrier Layers andManufacturing Method Therefor. U.S. Ser. No. 6,144,096 (Nov. 7, 2000.)

4. K. Ngan and S. Ramaswami. Method of Producing Smooth Titanium NitrideFilms Having Low Resistivity. U.S. Ser. No. 6,149,777 (Nov. 21, 2000).

5. T. Harada, S. Hirao, S. Fujii, S. Hashimoto, and M. Shishino. SurfaceModification of MOCVD-TiN Film by Plasma Treatment and SiH4 Exposure forCu Interconects. Materials Research Society Conference Proceedings ULSIXIV, pp. 329-335 (1999).

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objects and obtain the endsand advantages mentioned, as well as those inherent therein. It will beapparent to those skilled in the art that various modifications andvariations can be made in practicing the present invention withoutdeparting from the spirit or scope of the invention. Changes therein andother uses will occur to those skilled in the art which are encompassedwithin the spirit of the invention as defined by the scope of theclaims.

What is claimed is:
 1. A method of forming a titanium silicon nitridebarrier layer on a semiconductor wafer, comprising the steps of: (a)depositing a titanium nitride layer on the semiconductor wafer; (b)plasma-treating the titanium nitride layer in a N₂/H₂ plasma; and (c)exposing the plasma-treated titanium nitride layer to asilicon-containing gas ambient, wherein silicon is incorporated into thetitanium nitride layer as silicon nitride thereby forming a titaniumsilicon nitride barrier layer.
 2. The method of claim 1, wherein thedeposition of the titanium nitride layer comprises the steps of: (a)vaporizing a metalorganic titanium/nitrogen-containing compound; (b)introducing the vaporized titanium/nitrogen-containing compound into adeposition chamber of a CVD) apparatus; (c) maintaining the depositionchamber at a pressure and the wafer at a temperature suitable for thehigh pressure chemical vapor deposition of the titanium nitride layeronto the wafer; (d) thermally decomposing thetitanium/nitrogen-containing gas in the deposition chamber; and (e)vapor-depositing the titanium nitride layer onto the wafer.
 3. Themethod of claim 2, wherein the titanium nitride layer has a thickness ofabout 5 Å to about 100 Å.
 4. The method of claim 2, wherein themetalorganic titanium/nitrogen-containing compound comprisestetrakisdimethylamino titanium or tetrakisdiethylamino titanium.
 5. Themethod of claim 2, wherein the chamber pressure is from about 1 Torr toabout 10 Torr.
 6. The method of claim 2, wherein the wafer temperatureis from about 320° C. to about 370° C.
 7. The method of claim 1, whereinthe plasma treating step occurs at a plasma power of about 600W to about1500W.
 8. The method of claim 1, wherein the titanium nitride layer isplasma treated for about 4 seconds to about 40 seconds.
 9. The method ofclaim 1, wherein the silicon-containing gas comprises silane, disilane,methylsilane, or dimethylsilane.
 10. The method of claim 1, wherein theexposure to the silicon-containing gas ambient is from about 4 secondsto about 20 seconds.
 11. The method of claim 1, wherein a cycle of thesteps comprising depositing the titanium nitride layer andplasma-treating the deposited titanium nitride layer is repeated with nointervening step thereby depositing the titanium nitride layerincrementally prior to exposing the titanium nitride layer to thesilicon-containing gas ambient.
 12. A method of forming a titaniumsilicon nitride barrier layer on a semiconductor wafer, comprising thesteps of: (a) vaporizing tetrakisdimethylamino titanium; (b) introducingthe vaporized tetrakisdimethylamino titanium into a deposition chamberof a CVD apparatus; (c) maintaining the deposition chamber at a pressureof about 5 Torr and the wafer at a temperature of about 360° C.; (d)thermally decomposing the tetrakisdimethylamino titanium gas in thedeposition chamber; (e) vapor-depositing the titanium nitride film ontothe wafer; (f) plasma-treating the titanium nitride layer in a N₂/H₂plasma at a plasma power of about 750W for about 15 seconds wherein atitanium nitride layer having a thickness of about 25 Å is formed; (g)repeating steps (a) through (f) wherein a second titanium nitride layerhaving a thickness of about 25 Å is formed directly on the firstdeposited titanium nitride layer thereby forming a titanium nitridelayer having a total thickness of 50 Å; and (h) exposing theplasma-treated titanium nitride layer to a silane gas ambient for about10 seconds, wherein silicon is incorporated into the titanium nitridelayer as silicon nitride thereby forming a titanium silicon nitridebarrier layer.
 13. A method of improving the barrier performance of atitanium nitride layer comprising the steps of: introducing silicon intothe titanium nitride layer such that the silicon is incorporated intothe titanium nitride layer as silicon nitride wherein the barrierperformance of the titanium nitride layer is improved.
 14. The method ofclaim 13, wherein the introduction of silicon into the titanium nitridelayer as silicon nitride comprises the steps of: (a) vaporizing ametalorganic titanium/nitrogen-containing compound; (b) introducing thevaporized titanium/nitrogen-containing compound into a depositionchamber of a CVD apparatus; (c) maintaining the deposition chamber at apressure and the wafer at a temperature suitable for the high pressurechemical vapor deposition of the titanium nitride film onto the wafer;(d) thermally decomposing the titanium/nitrogen-containing gas in thedeposition chamber; (e) vapor-depositing the titanium nitride film ontothe wafer; (f) plasma treating the titanium nitride layer in a N₂/H₂plasma; and (g) exposing the plasma-treated titanium nitride layer to asilicon-containing gas ambient, wherein silicon is incorporated into thetitanium nitride layer as silicon nitride.
 15. The method of claim 14,wherein the metalorganic titanium/nitrogen-containing compound comprisestetrakisdimethylamino titanium or tetrakisdiethylamino titanium.
 16. Themethod of claim 14, wherein the silicon-containing gas comprises silane,disilane, methylsilane or dimethylsilane.
 17. The method of claim 14,wherein a cycle of the steps (d) through (f) is repeated with nointervening step thereby depositing a titanium nitride layerincrementally prior to exposing the deposited titanium nitride layer tothe silane ambient of step (g).
 18. A method of improving the barrierperformance of a titanium nitride layer comprising the steps of: (a)vaporizing tetrakisdimethylamino titanium; (b) introducing the vaporizedtetrakisdimethylamino titanium into a deposition chamber of a CVDapparatus; (c) maintaining the deposition chamber at a pressure of about5 Torr and the wafer at a temperature of about 360° C.; (d) thermallydecomposing the tetrakisdimethylamino titanium in the depositionchamber; (e) vapor-depositing the titanium nitride film onto the wafer;(f) plasma-treating the titanium nitride layer in a N₂/H₂ plasma at aplasma power of about 750W for about 15 seconds wherein a titaniumnitride layer having a thickness of about 25 Å is formed; (g) repeatingsteps (a) through (f) wherein a second titanium nitride layer having athickness of about 25 Å is formed directly on the first depositedtitanium nitride layer thereby forming a titanium nitride layer having atotal thickness of 50 Å; and (h) exposing the plasma-treated titaniumnitride layer to a silane gas ambient for about 10 seconds, whereinsilicon is incorporated into the titanium nitride layer as siliconnitride thereby improving the barrier performance of the titaniumnitride layer.
 19. A method of integrating copper into a semiconductordevice comprising the steps of: forming a titanium silicon nitridebarrier in a feature of the semiconductor device by the method of claim1; and depositing a copper layer over the titanium silicon nitridebarrier thereby integrating copper into the semiconductor device.
 20. Amethod of improving copper wettability at an interface of a copper layerand a titanium nitride layer in a semiconductor device comprising thesteps of: introducing silicon into the titanium nitride layer as siliconnitride by the method of claim 1 such that a titanium silicon nitridelayer is formed; and depositing a copper layer over the titanium siliconnitride layer wherein copper wettability at the interface of the copperlayer and the titanium silicon nitride layer is improved over copperwettability at the copper/titanium nitride interface.